How is intrinsic Positive End-Expiratory Pressure (PEEP) managed in patients with Chronic Obstructive Pulmonary Disease (COPD) or asthma?

Management of Intrinsic PEEP in COPD and Asthma Patients

Intrinsic PEEP (PEEPi) in patients with COPD or asthma should be managed by optimizing ventilator settings with longer expiratory times, lower respiratory rates, and applying external PEEP at levels below the measured PEEPi to reduce work of breathing without causing further hyperinflation. 1

Understanding Intrinsic PEEP

• Intrinsic PEEP (auto-PEEP) develops when the time required for lungs to decompress to elastic equilibrium volume is shorter than the available expiratory time before the next breath 1
• PEEPi acts as an inspiratory threshold load that must be overcome by the patient's inspiratory muscles before triggering a breath, increasing work of breathing 1
• In COPD and asthma, airflow limitation during expiration leads to dynamic hyperinflation and development of PEEPi 1
• This end-expiratory recoil pressure creates an additional workload for respiratory muscles and can impair inspiratory muscle function 1

Clinical Consequences of Intrinsic PEEP

• Increased work of breathing as patients must generate greater negative pressure to trigger the ventilator 1
• Ineffective triggering efforts and patient-ventilator asynchrony 1
• Hemodynamic compromise due to decreased venous return and reduced cardiac output 2
• Risk of barotrauma from hyperinflation 1
• Hypotension due to impaired venous return 1
• Increased risk of respiratory muscle fatigue 1

Detection and Measurement

• PEEPi can be measured using the end-expiratory airway occlusion technique 1
• This can be performed manually at the expiratory port of the ventilator during the last 0.5 seconds of expiration 1
• Alternatively, simultaneous recording of flow and pleural pressure can be used 1
• Clinical signs suggesting PEEPi include patient-ventilator asynchrony, unexplained hypotension, and difficulty triggering breaths 1

Management Strategies

Ventilator Settings Optimization

• Decrease respiratory rate to allow more expiratory time (10-15 breaths/min in COPD) 1
• Use shorter inspiratory times with higher flow rates (80-100 L/min) 1
• Aim for longer expiratory times with I:E ratios of 1:4 or 1:5 1
• Reduce tidal volumes to 6-8 mL/kg to minimize hyperinflation 1
• Consider permissive hypercapnia (maintaining pH >7.2) to reduce the risk of barotrauma 1

Application of External PEEP

• Apply external PEEP at levels below the measured PEEPi (typically 80-90% of measured PEEPi) 1
• This reduces the inspiratory threshold load without causing additional hyperinflation 1
• Setting PEEP greater than PEEPi is harmful and can worsen hyperinflation 1, 3
• External PEEP can improve patient-ventilator synchrony and reduce work of breathing 1

Pharmacological Interventions

• Continue bronchodilator therapy to reduce airway resistance 1
• Administer bronchodilators through the endotracheal tube if the patient is intubated 1
• Consider adequate sedation to optimize ventilation and decrease ventilator dyssynchrony 1

Managing Complications

• If auto-PEEP results in significant hypotension, disconnect the patient from the ventilator circuit temporarily to allow PEEP to dissipate during passive exhalation 1
• Assist with exhalation by pressing on the chest wall after disconnection if hypotension is severe 1
• Check for pneumothorax if there is sudden deterioration 1
• Use the "DOPE" mnemonic (tube Displacement, tube Obstruction, Pneumothorax, Equipment failure) plus auto-PEEP to troubleshoot deterioration in intubated patients 1

Special Considerations

• In severe cases with persistent patient-ventilator dyssynchrony despite adequate sedation, paralytic agents may be considered 1
• During cardiac arrest in asthmatic patients, consider brief disconnection from the ventilator and chest wall compression to relieve air-trapping 1
• For patients with neuromuscular disease, lower inflation pressures (10-15 cmH2O) are typically sufficient, whereas patients with chest wall deformity require higher pressures 1

By implementing these strategies, clinicians can effectively manage intrinsic PEEP in patients with COPD and asthma, reducing work of breathing and minimizing complications associated with dynamic hyperinflation.